The Blurred Lines of Driving While Stoned
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The Blurred Lines of Driving While Stoned


Driving under the influence is about to get a whole lot more complicated with legal pot dispensaries popping up on every corner. So how stoned is too stoned to drive, and how can cops test just how stoned drivers actually are?

The Ball’s In Your Court, Vermont

That’s the question Vermont legislators are facing this week. On Monday the state Senate gave preliminary approval to a new bill about driving under the influence of drugs. The bill aims to compromise with the version proposed by the House, which defines “under the influence” to mean that “a person’s full mental or physical abilities are diminished or impaired to the slightest degree.” That’s actually how it’s already defined for alcohol, except with the latter there’s a much clearer index of impairment: that magic number we’ve all got memorized, 0.08. Since such a golden ratio doesn’t exist yet for other drugs, the House bill basically constitutes a zero-tolerance policy. According to the Senate, that’s simply unfair, since some drugs don’t interfere with driving and may even improve it. As a compromise, the Senate bill’s new language draws a line when drugs “interfere with a person’s safe operation of a vehicle in the slightest degree.” By contrast, current standards define the illegal influence of drugs to be “a degree which renders the person incapable of driving safely.” This is just too vague and too high a bar according to the bill’s proponents (largely prosecutors and police).

Driving under the Influence…of Anything

Given that marijuana (medical or otherwise) is becoming legal in more and more states, the motive behind this legislation seems sound. I don’t think I’m going to sound like Nancy Reagan when I say that pot, while harmless at home, can pose a risk behind the wheel. Argue all you want that hitting the bong actually makes you a better driver. Maybe it really does amplify your concentration—I mean, dude, have you ever really looked at the road? I mean really looked at it? But common sense dictates that there is some quantifiable amount of any mind-altering substance that makes driving unsafe, and it’s better to be safe than sorry.

Of course, not all drugs are created equal, and by using “drugs” as a blanket term, lawmakers are making the problem more complicated than it needs to be. How much cocaine is okay to drive on? How much Percocet? How much acid (well okay, probably none)? Thankfully, most of these questions have logical answers, at least in the short term. The impact of prescription drugs on driving has ostensibly already been studied, which is why so many of them come with those warning stickers about “operating heavy machinery.” And for drugs that are flat out illegal to possess, a zero tolerance policy for drivers is at least legally consistent if not necessarily scientifically supported.

Pot’s Effects Vary

Unfortunately, the one drug that poses the biggest challenge to regulate is also the one that the bill is really about. Marijuana comes in so many strains and produces such varied effects in different people that measuring its effect on driving is a tall order in itself. For some people, pot seems to work a lot like alcohol, which could lead to slower reaction times (though potentially less road rage). For others it can cause mild distortions of reality, and while that’s fine for hanging out in a hammock watching the sun set over the Green Mountains, it doesn’t work so well when merging on to the 91. Drug recognition experts can tell when a driver’s been smoking, but as of now— unless unsafe driving has already been demonstrated—there’s no way to prove how high is too high.

The Vermont Senate is concerned that different drugs need to be factored into the driving laws, but they have enough on their plate just determining the safety of cannabis. By contrast, California is using more quantitative measurements to assess marijuana intoxication, although with little progress so far. Last week a bill failed that would have made it a DUI to have as little as two nanograms per milliliter of THC metabolites in the blood. That’s less than half of the five nanograms per milliliter that will get you a conviction  in Washington and Colorado, but hey, at least it’s a number. The trouble with such low limits, medical pot advocates argue, is that THC shows up in drug tests for weeks after the high has worn off. This is a valid point that demands more research, but at least Colorado and Washington’s limits are measurable. With pot on the path to widespread legality, it’s high time it got its own magic number for the road.

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About Author

Erica Larsen AKA Eren Harris blogs at Whitney Calls and Clean Bright Day. Their writing has also been published on Salon, Selfish, Violet Rising and YourTango. They live in Los Angeles with their husband and their enormous cat.